Castable high explosive of cyclotetramethylenetetranitramine and dodecenyl succinic anhydride-vinyl cyclohexene dioxide polymer binder

ABSTRACT

This invention relates to a castable explosive composition of the non gelatinized type in which cyclotetramethylenetetranitramine is the chief constituent.

United States Patent [1 1 Voreck et a1.

[ 1 Apr. 29, 1975 [75] Inventors: Wallace E. Voreck; James R. Sides,

both of Asheville, NC.

[73] Assignee: The United States of America as represented by the Secretary of the Navy, Washington, DC.

[22] Filed: Nov. 13, 1963 [21] Appl. No.1 323,515

[52] US. Cl. l49/l9.5; 149/19.92; 149/20; 149/92; 149/21; 149/115 [51] Int. Cl C06b 15/02 [58] Field of Search..... 149/19, 92, 44, 19.5, 19.92, 149/20, 24, 115, 38; 260/78.4 EP, 18 EP [56] References Cited UNITED STATES PATENTS 3,116,186 12/1963 Paul 149/92 X 3,116,189 12/1963 Fisher 149/92 3,117,044 l/1964 Sauer 3,117,099 1/1964 Proops et a1. 260/18 EP OTHER PUBLICATIONS Lee and Neville, Epoxy Resins, pp. 134-135, McGraw-Hill Book Company, Inc. (1957), New York, TP 986.136 L4.

Primary Examiner-Benjamin R. Padgett Assistant ExaminerE. A. Mi1ler Attorney, Agent, or Firm-R. S. Sciascia; Henry Hansen [57] ABSTRACT This invention relates to a castable explosive composition of the non gelatinized type in which cyclotetramethylenetetranitramine is the chief constituent.

5 Claims, No Drawings CASTABLE HIGH EXPLOSIVE OF CYCLOTETRAMETHYLENETETRANITRAMINE AND DODECENYL SUCCINIC ANHYDRIDE-VINYL CYCLOI-IEXENE DIOXIDE POLYMER BINDER BACKGROUND OF THE INVENTION Castable explosives have the ability to be readily formed into any desired configuration at a certain processing temperature. The explosive solids in a castable composition are carried by a high viscosity liquid binder which becomes pourable at the processing temperature. The problem with this type of castable explosive was that it possessed both poor thermal stability and poor high temperature properties because of the fact that it melted when heated.

An object of this invention is to provide a high melting castable explosive composition that possesses a binder having sufficiently low viscosity to allow a high solids loading and which upon cure has good high temperature properties.

Yet another object of this invention is to provide a high melting thermoset compatible composition which possesses water and chemical resistant self-supporting explosive characteristics in addition to high heat resistance and good electrical characteristics and which retains its plasticity and explosive characteristics after prolonged exposure to adverse conditions.

A still further object of this invention is to provide a high melting castable composition which is easily and safely manufactured in conventional melting, mixing, casting and curing equipment.

Other objects will become apparent as the invention is further described.

We have discovered that the foregoing objects can be achieved when we provide an explosive composition comprising at least 63 percent by weight of cyclotetramethylenetetranitramine particles having a maximum dimension of 58 to 400 microns. A typical formulation contains 84 percent by weight cyclotetramethylene tetranitramine, 10.6 percent by weight of vinylcyclohexene dioxide, 5.4 percent by weight of dodecenyl succinic anhydride and 0.02 0.08 percent by weight of stannous octoate. This compound, when cured, has a density of 1.67 1.70 grams/cc, a compressive strength of 3500 psi, a compressive modulus of 1 X 10 psi, a coefficient of expansion of 1.17 X inlinF and is thermally stable for 48 hours at 350F.

Numerous attempts have been made in the past to discover a liquid binder that would serve the dual function of having a sufficiently low viscosity to allow a high solids loading and which upon cure would form a thermoset compound. TNT has been, heretofore, widely used as the liquid binder for castable explosives; however, at temperatures of 350F, the TNT explosive mixture would melt thereby rendering the explosive charge ineffective. Consequently, we turned to other materials to replace the TNT as a binder.

We believe that vthe selection of an epoxideanhydride system to function as a binder in castable explosives wherein it is completely compatible with the other explosive components and wherein it is able to overcome the disadvantages of other types of binders represents an essential aspect of this invention in addition to the highly advantageous properties of the selfsupporting plastic composition made possible thereby.

The epoxide, vinylcyclohexene dioxide, was particularly favorable due to its low viscosity of 7.8 centipoises at 20C. Sixty-six per cent by weight of vinylcyclohexene dioxide was mixed with 34 percent by weight of dodecnyl succinic anhydride and was cured in an oven for 18 20 hours at 200 266F in the presence of a catalyst such as stannous octoate.

The pot life of this low viscosity epoxy binder is over 2 hours at 203F, and over 8 hours at 149F with 0.15 percent by weight of stannous octoate catalyst. lt can be reduced further with more catalyst if a shorter cure time is desired. Because of the long cure time, exothermic reactions cause no problems in pot life or overheating during cure. Viscosity is very low, approximately 8 centipoises, thereby permitting high solids-loaded pourable mixes. The polymer formed is plasticized by the dodecenyl succinic anhydride thereby minimizing problems of cracking during thermal cycling. Thermal stability of the polymer is excellent at 392F whereby failure of the explosive component, not the binder, sets the upper temperature limit of the cast explosive.

In addition to the density, viscosity and concentration of the binder, castability depends upon the proper solids particle size distribution of the cyclotetramethylenetetranitramine. We have found that the particle size of this cyclotetramethylenetetranitramine must be of such size that its maximum dimension is within the range of 58 to 400 microns. The optimum ratio of coarse to fine particles of the solid phase for maximum packing fraction is 25. If explosive component is less than 58 micron size, it becomes too dry and uncastable. If it exceeds 400 micron size, the sensitivity of the composition is increased to such an extent that the compositionis of little value. I

The following examples serve to illustrate specific embodiments and advantageous features of the castable explosive composition of the present invention. However, they will be understood to be illustrative only and not as limiting the invention in any manner. Parts given in the examples are parts by weight unless otherwise specified. All the drop test results reported in the examples were obtained using; a 20 drop Bruceton test with a 2 kgm hammer and Type 12 Tooling (Flat Anvil and Striker, sample on sandpaper) made according to the droptest apparatus described in Bureau of Mines Bulletin 346 [Monroe and Tiffany, p. 72 (1931)].

EXAMPLE I 10.6 grams of vinylcyclohexene dioxide was introduced into a mixer and brought to a temperature of about 150 166F. Then 5.4 grams of dodecenyl succinic anhydride was mixed with the dioxide. Large particles of cyclotetramethylenetetranitramine in the range of 400 microns particle diameter were formed by recrystallizing the solids from a solution of cyclohexanone and passing it over a No. 40 mesh screen. Small particles of the nitramine in the range of 58 microns particle diameter were recrystallized by quenching an acetone solution in water and passing it over a No. 325 mesh screen. Twenty-one grams of the nitramine, having a particle size of 58 microns in diameter, and 63 grams of the nitramine, having a particle size of 400 microns in diameter were added to the mixture. The whole mixture was heated to 150 200F in an evacuated mixer to reduce its viscosity during casting. The mixture is then poured into a curing mold after which it is cured at 200 220F for 24 hours.

The cured explosive had a uniform density of 1.67 1.70 grams/cc and was initiated in the beforementioned drop test by the drop of a 2 kg. weight from a height of 35 cm. The composition was stable for 48 hours at 350F, stable for at least 5 minutes at 425F and explodes in five seconds at 480F.

The detonation velocity was determined on a V2 inch diameter unconfined charge having a density of 1.69 grams/cc. Five 3 inch long charges are clamped in a stack and initiated by a detonator and tetryl booster pellet. Transit time across each pellet is determined by foil switches made of 0.002 thick mylar film aluminized on both sides. Lengths are measured with a micrometer. The composition had a detonation velocity of 8,160 meters/sec.

Stannous octoate can be added to the mixture to decrease its pot life and also to catalyze the reaction of the dioxide with the anhydride.

EXAMPLE 11 A castable explosive composition was blended according to the method described under Example I. It contained the following ingredients:

58.7% 400 micron particle size cyclotetramethylenetetranitramine 6.0% 54 micron particle size cyclotetramcthylenetetranitramine 19.3% 30 micron chromatc inhibited aluminum particles 10.5% vinylcyclohexene dioxide 5.4% dodecenyl succinic anhydride 0.1% stannous octoate This composition was stable at 338F for 48 hours and at 464F for two minutes. The cured explosive had a uniform density of 1.734 grams/cc with a detonation velocity of 7,638 meters/sec. 1n the drop hammer test, this composition produced 0.1 percent fires at 37 cm. 0.50 percent tires at 47 cm and 99.9 percent fires at 60 *An inhibited aluminum powder is one employing a thin film of chromium salt to protect the aluminum from reactive materials.

The present invention has been described in detail in the foregoing. However, it will be apparent to those skilled in the art that many variations are possible without departure from the scope of the invention. Therefore, we intend to be limited only by the following claims.

We claim:

1. A castable explosive composition having a polymerized plastic binder consisting essentially of the following constituents:

Constituent: Per Cent By Weight Cyclotetramethylenetetranitramine having a maximum particle dimension within the range of 58 to 400 microns Polymerized plastic binder said polymerized plastic binder consisting essentially of:

Constituent: Per Cent By Weight C yclotctramethylenetetranitramine 400 micron particle size 63 Cyclotetramethylenetetranitramine 58 micron particle size 21 P01 merized plastic binder l6 sai polymerized plastic binder consisting essentially of:

Constituent: Per Cent By Weight Vin lcyclohexene dioxide 10.6

ecenyl succinic anhydride 5.4.

3. A castable explosive composition having a polymerized plastic binder consisting essentially of the following constituents:

Constituent: Per Cent By Weight Cyclotetramethylenetetranitramine 400 micron particle size 63 Cyclotetramethylenetetranitramine 58 micron particle size 21 Polymerized plastic binder 15 16 Stannous octoate Less than 0.1

said polymerized plastic binder consisting essentially of:

Constituent: Per Cent By Weight Vin lcyclohexene dioxide 10.6 Do ecenyl succinic anhydride 5.4.

4. A castable explosive composition having a polymerized plastic binder consisting essentially of the following constituents:

Constituent: Per Cent By Weight Cyclotetramethylenetetranitramine over 150 micron particle size Cyclotetramethylenetetranitramine less than micron particle size Atomized inhibited aluminum less than 30 micron particle size Pol merized plastic binder sat polymerized plastic binder cons|sting essentially of:

Constituent: Per Cent By Weight Vincylcyclohexene dioxide 10.5

Do ecenyl succinic anhydride 5.4 Stannous octoate Less than 0.1.

5. A method for preparation of a castable high melting explosive composition which comprises the following steps, viz.

a. mixing at least 10.6 percent by weight of vinylcyclohexane dioxide with at least 5.4 percent of dodecnyl succinic anhydride at a temperature of 166F;

b. adding at least 63 percent by weight of cyclotetramethylenetetranitramine having a maximum particle dimension within the range of 58 400 microns to the said mixture;

c. incorporating less than 0.1 percent stannous octoate in the mixture;

d. maintaining the mixture at a temperature between 150 to 200F; and

e. pouring the mixture into a curing mold at a temperature of 200 220F wherein after twenty-four hours a thermoset castable high melting point ex-- plosive composition is formed. k 

2. A castable explosive composition having a polymerized plastic binder consisting essentially of the following constituents:
 3. A castable explosive composition having a polymerized plastic binder consisting essentially of the following constituents:
 4. A castable explosive composition having a polymerized plastic binder consisting essentially of the following constituents:
 5. A method for preparation of a castable high melting explosive composition which comprises the following steps, viz. a. mixing at least 10.6 percent by weight of vinylcyclohexane dioxide with at least 5.4 percent of dodecnyl succinic anhydride at a temperature of 150* - 166*F; b. adding at least 63 percent by weight of cyclotetramethylenetetranitramine having a maximum particle dimension within the range of 58 - 400 microns to the said mixture; c. incorporating less than 0.1 percent stannous octoate in the mixture; d. maintaining the mixture at a temperature between 150* to 200*F; and e. pouring the mixture into a curing mold at a temperature of 200* - 220*F wherein after twenty-four hours a thermoset castable high melting point explosive composition is formed. 